Low-grade myofibroblastic sarcoma arising in the tip of the tongue with intravascular invasion: A case report.

Low-grade myofibroblastic sarcoma (LGMS) is a rare intermediate tumor, which rarely metastasizes and has myofibroblastic differentiation in various sites. It is particularly associated with the tongue in the head and neck region. The lack of any pathological features means it is difficult to make a conclusive diagnosis of LGMS. The immunohistochemical features and genomic rearrangements, including SS18-SSXs and MYH9-USP6s and the genetic mutations of cancer-associated genes, including APC, CTNNB1, EGFR, KRAS, PIK3CA and p53 were examined in a case of LGMS arising in the tip of the tongue. Immunohistochemically, the tumor cells were positive for alpha-smooth muscle actin and vimentin, as in previous reports. They demonstrated neither genomic rearrangements nor point mutations of cancer-associated genes. Although several tumor cells demonstrated intravascular invasion, the MIB-l labeling index of the cells was the same as the original lesion. To the best of our knowledge, this is the first case report of LGMS arising in the tip of the tongue with intravascular invasion.